Patent GB-813263-A (GB)
Title: Improvements in or relating to planing machines
IPC: B23Q5/26
Filed: 1955-08-18
Abstract: 813,263. Planing-machines. KLOPP, F. Aug. 18, 1955 [Sept. 11, 1954], No. 23856/55. Class 83 (3). [Also in Group XXIX] In an hydraulically-controlled planing-machine, in order to reduce "screen marks" during planing, oil discharged from the working cylinder during a working roughing-stroke is throttled, the size of the throttle-aperture being set automatically in dependence upon the cutting pressure, but not decreasing due to fluctuations in that pressure. A pump 14 supplies liquid through a reversing valve 10 to either side of a piston 39 connected to the worktable. The position of the valve 10 is controlled by liquid supplied through a pilot-valve 2, the pilot-valve being controlled by abutments 4, 5 on the work-table. A valve 13 is set in the position shown for planing, and moved to the left for finishing. Rotation of valve 13 through 90 degrees by-passes the pumpdelivery to a reservoir 64. Rough-planing, forward-stroke.-The valves are in the positions shown, and liquid is supplied by the pump, via valves 2, 10 and a line 37 to one side of the working cylinder, and discharged from the other side through a line 41 to a space 44 around the valve 10, thence through ports 45 and various ducts and a checkvalve 63 to the reservoir 64. An annularpiston 69 sliding on the valve member 10 partially closes the ports 45, a face 68 of the piston being exposed to the pump pressure which moves the piston 69 downwardly until a balance is reached with the pressure in space 44. The oil discharged from the working- cylinder is thus throttled. A space 70 behind the piston 69 is supplied with liquid at a lowpressure determined by the check-valve 63, a non-return valve 82 preventing the discharge of liquid from the space 70, and thus preventing the piston 69 from increasing the size of the passage through the ports 45 due to any fluctuation in the cutting pressure. Return stroke.-The pilot-valve 2 is moved downwardly by the abutment 5 and prevents the discharge of liquid through the line 41. Pump pressure builds up, and is directed to a chamber 89 at the upper end of the valve 10 to move it downwardly, the chamber 28 at the lower end being open to exhaust. Movement of the valve 10 opens the space 70 to exhaust so that piston 69 can move to its uppermost position. Oil is now supplied to the working- cylinder through line 41, and is discharged through line 37 unimpeded, apart from a slight resistance due to valve 63, to the reservoir. At the end of the return stroke the pilot-valve 2 is moved upwardly and oil is supplied to the chamber 28 and exhausted from the chamber 89 to move the reversing-valve 10 upwardly and the cycle repeats. Finishing-stroke.-Valve 13 is moved downwards. With the pilot-valve in its uppermost position, oil is supplied to the chamber 28 and exhausted from the chamber 89 to move the reversing-valve 10 upwardly and oil is supplied to both sides of the piston 39. The piston is moved on its forward stroke owing to the differential areas. The return stroke is as before. In a modification the throttling of the oil discharged during roughing is obtained by the means shown in Fig. 5. Openings 143, 144, lie in line 41 and a piston 131 throttles the passage between the openings. On a forwardstroke during roughing, a connection 147 communicates with the pump, a member 136 is moved to the right, and liquid admitted to a surface 132 of the piston 131 to move it to the right to a throttling position. Oil upstream of the valve 63 is admitted, through a non-return valve 146, to a space behind a surface 133 to prevent the piston 131 moving to the left due to fluctuating cutting-pressure. On the returnstroke, connection 147 communicates with the discharging oil, and the oil supplied by the pump flows through connections 144, 143 and forces the member 136 to the left. The space behind surface 133 is thus opened to a discharge line 142 so that piston 131 can move to the left.